Lock sets and latch sets for securing doors in their closed position are installed in the fabric of the door itself. It is a requirement that the latch bolt extends through the edge of the door to be received in an aligned recess in a door frame. The door handles extend perpendicularly to the latch bolt so as to manipulate a coupling mechanism to release the latch bolt from the recess in the door frame when it is required to open the door. The lock set version has a locking mechanism for locking the latch bolt when the door is closed. For internal doors the locking mechanism is not required and thus a latch set and not a lock set is provided. The door itself is therefore required to have a passageway through the major surfaces of the door extending normally to the passageway leading to the door edge for the latch bolt. In the past the passageway for the latch bolt and the passageway for the latch set handles have been drilled. The latch bolt passageway is drilled by drilling a hole into the edge of the door and the latch set handle passageway is produced by drilling a hole normally to the first passageway through a side surface of the door. In addition it is well known that the latch bolt has a case which at its outer end has a plate to be located in a recess at the door edge. Usually this recess is formed after the latch bolt passageway has been drilled. The recess to receive the latch bolt case plate ensures that the latch bolt case is properly located in the door frame such that a flat face on the latch bolt is correctly aligned with the major plane of the door, that is the plane of its side faces. In addition the latch bolt case plate is provided with means for securing the locks case in the door itself.
This construction has the disadvantage that the formation of the plate receiving recess which is accomplished by a carpenter on site, usually involves labor time in the order of 30 to 45 minutes. This is expensive labor time as there are usually a number of latch sets or lock sets to be fitted in each house on a building development. Typically, there will be at least seven latch sets per house. The formation of the recess is usually by means of hammer and chisel since the recess is formed by the removal of the relevant portion of the door which is completely bounded. It is therefore not possible to remove the wood by sawing.
Accordingly, the present invention has an object, the provision of a latch bolt case which does not require a plate to be inserted in a door edge recess, but which is readily aligned such that the flat face of the latch bolt is parallel to the major face of the door.
It is a further object of the invention to provide a latch bolt case which is readily and speedily fitted in a latch bolt case passageway which has simply to be drilled.
It is a further object of the invention to provide a latch case which is provided with self-retaining means when inserted in a latch bolt case passageway.
It is a further object of the present invention to provide a drilling jig assembly which enables the passageways for the latch bolt and the latch set handles to be speedily formed with the correct alignment and which then enables the latch bolt case to be speedily positioned with the correct alignment.
It is a further object of the invention to provide an improved method of installing a lock case in a door which avoids the lengthy use of carpenters time subsequent to the formation of the drilled passageways in the door.